Introduction

Stress urinary incontinence (SUI) is a common health problem in women and is characterized by complaints of involuntary urinary release during exertion, sneezing, or coughing. SUI is accompanied by a significant reduction in quality of life, sexual function, and psychological and social health [1]. Currently, suburethral slings (tapes) are considered the standard surgical method for the treatment of SUI among women [2]. Two main groups of slings are available: standard mid-urethral slings (SMUS) and single-incision mini-slings (SIMS). Each includes different slings with adjustable tapes that are included in both groups. The SMUS is available with retropubic and transobturator-placed tapes. The two types of slings have shown comparable effectiveness, but the complication profiles are different [3]. The international debate regarding the safety of these methods has resulted in court actions in Canada, the USA, the UK and some European countries against the use of vaginal approaches employing slings and tapes [4]. SIMS is also available with several different tapes that have various properties, especially in terms of adjustability, type of fixation, and sling length. The comparative efficacy of SMUS and SIMS remains unclear [5].

The low probability of postoperative voiding dysfunction can be considered the main advantage of adjustable slings. In the published literature, 27.3 to 46.8% of women need tension adjustment [6, 7]. Up to 21.3% of women need a reoperation for urinary retention or voiding dysfunction after TOT, with insufficient tensioning of the tape considered a failure of surgery [8]. Adjustable SIMS and SMUS allow control of the tension of the tape, which in turn can reduce postoperative risk [9]. Some SMUS can also be adjusted in the early postoperative period and even over the life of the patient [10]. Several studies have compared various adjustable SIMS with other slings [11]. The aim of this study is to evaluate the efficacy and safety of different adjustable slings compared to other surgical methods for the treatment of SUI among women.

Materials and methods

The present systematic review included all published research articles that evaluated the effectiveness of adjustable slings compared with other surgical methods in terms of quality of life in patients with SUI. The secondary outcome measures were postoperative complications and safety. Our systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 checklist [12].

Institutional review board (IRB) approval was not requested, as this study is a review of published studies. The present systematic review has been registered in the PROSPERO international prospective register of systematic reviews of the National Institute for Health Research (NIHR). The registration number is PROSPERO 2022 CRD42022369785 [13]. The PubMed, MEDLINE and Cochrane Library databases were searched up to November 2022 to identify relevant trials. The search used a combination of the following terms: “adjust,” “sling,” “tape,” “ajust,” “altis,” “remeex,” and “female.”

The search was conducted independently by two investigators (G.S. and B.G). Following the search, all articles were screened based on their titles and abstracts. The full texts of the remaining studies were then reviewed. The reference lists of eligible trials were also manually searched to identify additional potential studies. Two investigators (G.S. and B.G.) independently read the full texts of the articles to determine the eligibility of the articles based on the presence of comparisons between adjustable slings and any other surgical methods for SUI. Studies were excluded if there were duplicate datasets. All disagreements concerning the inclusion or exclusion of a preselected study, as well as other disagreements during the review process, were resolved by consulting a third author (G.K.). The included studies were independently assessed using a standardized data extraction procedure (authors, publication year, study design, patient characteristics, intervention, and outcomes).

The main purpose was to evaluate the objective and subjective effectiveness of achieving better continence and quality of life for women with SUI. Subjective effectiveness was analyzed as a dichotomous variable (effective and noneffective) based on the patient's subjective opinion after treatment, thus affecting the quality of life. The secondary aim was safety assessment.

The inclusion criteria were as follows: clinical studies (randomized controlled trials [RCTs] and non-RCTs that included a minimum of 10 patients) assessing adult women with a clinically confirmed diagnosis of SUI; and articles written in English. The exclusion criteria were as follows: studies that included patients with other types of urinary incontinence; studies that combined conservative interventions and pharmacological treatment; pregnant and lactating patients; and conference abstracts and unpublished papers. A risk-of-bias assessment was conducted for each of the studies included based on the Cochrane Handbook for Systematic Reviews of Interventions [14]. Two investigators (G.S. and B. G) independently assessed the quality of the selected studies. A third investigator (G.K.) was consulted when disagreements occurred. In accordance with the Cochrane Handbook for Systematic Reviews of Interventions, the revised risk-of-bias tool for randomized trials (RoB 2) [15] was used to assess the risk of bias in RCTs, and the ROB tool for non-randomized studies of interventions (ROBINS-I) [16] was used for non-randomized studies (prospective controlled, prospective cohort, retrospective studies, and other types of studies). These tools were also used to assess the risk of bias arising from reporting bias due to missing synthesis results. The data were pooled in a meta-analysis using RevMan software (Review Manager version 5.4, The Cochrane Collaboration, 2011).

Results

The authors searched the PubMed, MEDLINE, and Cochrane Library databases and initially retrieved 1385 articles (Fig. 1). After removing duplicates and screening the titles and abstracts of the articles, 51 publications were subjected to full-text review. Of these, 33 articles were excluded after reading the full texts: five studies were reviews, one article was an RCT protocol [17]; four studies were not in English; and 23 studies lacked relevant inclusion criteria. The studies without appropriate inclusion criteria (n = 23) included 19 studies that did not compare interventions; one study that assessed a health economic evaluation [18]; one RCT that compared the MiniArc SIMS with TVT [tension-free vaginal tape] Abbrevo [19]; one study that evaluated the efficacy of intraoperative extrinsic manual bladder compression for TOT adjustment in MUS [20]; and one cohort study that compared a single-incision sling with a retropubic mid-urethral sling [21].

Fig. 1
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Flow diagram

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In addition, the references of the selected articles were checked for potentially eligible studies (n = 384). The authors selected 47 articles for full-text review, but 45 of them were duplicates, and two publications were excluded due to noncompliance with our criteria. Ultimately, 18 clinical trials were included in our systematic review, and 11 were included in the meta-analysis. Fourteen articles were RCTs, and four were retrospective studies. In one RCT, the authors simultaneously compared three types of interventions: TVT-O, MiniArc SIMS and Ajust SIMS (Table 1). In addition, among the articles found, one RCT [22] and one retrospective comparative study [23] compared transobturator adjustable tape (TOA) with TOT, and one RCT [24] compared suburethral adjustment-controlled tape (SACT) with TOT mid-urethral sling (Table 2). Only RCTs were included in the meta-analyses.

Table 1 Description of the studies included in the systematic review (adjustable mini-slings)
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Table 2 Description of the studies included in the systematic review (non-adjustable mini-slings)
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The first meta-analysis was focused on the subjective cure rate in adjustable single-incision mini-slings and standard mid-urethral slings after the intervention. In this meta-analysis, nine studies evaluating 1400 patients were included (RR = 1.02, 95% CI: [0.97, 1.06], p = 0.50). The level of heterogeneity for this comparison was 0%. There was no statistically significant difference. Consequently, adjustable SIMS did not show any effectiveness over SMUS in subjective improvement of SUI symptoms (Fig. 2).

Fig. 2
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A Subjective cure rate in adjustable SIMS and SMUS, B Subjective cure rate in Ajust SIMS vs. MiniArc SIMS

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The second analysis focused on the subjective cure rate in Ajust SIMS and MiniArc SIMS. In this meta-analysis, two studies evaluating 143 patients were included (RR = 0.96, 95% CI: [0.86, 1.06], p = 0.41). The level of heterogeneity was 0%. As a result, there was no statistically significant difference between Ajust SIMS and MiniArc SIMS in subjective cure rate. Nevertheless, due to the lack of dichotomous data, only two trials were eligible for this comparison.

The third analysis aimed to compare adjustable SIMS versus SMUS in objective cure rate. The authors included 10 studies assessing 1596 patients in this meta-analysis (RR = 0,99, 95% CI: [0.96, 1.02], p = 0.61). The level of heterogeneity was 0%. There was no statistically significant difference in objective cure rate between Ajust SIMS and SMUS (Fig. 3).

Fig. 3
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A Adjustable SIMS vs. SMUS in objective cure rate, B Ajust SIMS vs. MiniArc SIMS in objective cure

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In the fourth analysis, the authors compared Ajust SIMS and MiniArc SIMS with respect to the objective cure rate. The next meta-analysis included only two studies involving 143 patients (RR = 0.97, 95% CI: [0.87, 1.07], p = 0.51). The level of heterogeneity was 0%. There was no statistically significant difference.

In the fifth analysis, the authors included six studies involving 764 patients to compare the long-term postoperative complication rates between adjustable SIMS and SMUS (RR = 0.49, 95% CI: [0.08, 2.92], p = 0.43). The level of heterogeneity was 53%. The meta-analysis revealed that there was no statistically significant difference (Fig. 4).

Fig. 4
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A Long-term postoperative complications in adjustable SIMS and SMUS, B Adjustable SIMS vs. SMUS in de novo urgency

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The sixth analysis compared the level of de novo urgency between adjustable SIMS and SMUS. In this meta-analysis, seven studies assessing 866 patients were included (RR = 1.53, 95% CI: [0.93, 2.52], p = 0.10). The level of heterogeneity was 0%. There was no statistically significant difference in this comparison.

The seventh analysis included five studies with 787 patients to compare vaginal tape erosion between adjustable SIMS and SMUS (RR = 0.93, 95% CI: [0.20, 4.37], p = 0.93). The level of heterogeneity for this comparison was 17%. No statistically significant differences were found in this comparison (Fig. 5).

Fig. 5
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A Adjustable SIMS vs. SMUS in vaginal tape erosion, B Operation time of adjustable SIMS vs. SMUS

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The eighth analysis compared the operation time between adjustable SIMS and SMUS. Five studies assessing 895 patients were included in this meta-analysis. The operation time of adjustable SIMS was significantly lower (RR = −4.20, 95% CI: [−7.51, −0.89], p = 0.01). The level of heterogeneity for this comparison was 97%.

Two reviewers (G.S. and B.G.) evaluated the risk of bias in each of the studies included according to the Cochrane Handbook using RoB 2 for RCTs and ROBINS-I for non-RCTs. Any disagreements were resolved by a third reviewer (G.K.). The visualization tools were created by the Risk-Of-Bias VISualization (ROBVIS) app [39]. This app created “traffic lights” plots of the domain-level judgments for each result and weighted bar plots of the distribution of risk-of-bias judgments within each bias domain. Two non-RCTs had a moderate risk of bias, one serious and one critical, according to the ROBINS-I instrument (Figs. 6 and 7). Additionally, based on the RoB 2 instrument (Figs. 8 and 9), two randomized trials were at a high risk of bias, eight had some concerns, and four were at a low risk of bias.

Fig. 6
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ROBINS-I tool for non-randomized studies of interventions (traffic light plot)

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Fig. 7
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ROBINS-I tool for non-randomized studies of interventions (summary plot)

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Fig. 8
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RoB 2.0 tool for randomized controlled trials (traffic light plot)

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Fig. 9
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RoB 2.0 tool for randomized controlled trials (summary plot)

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Discussion

This systematic review and meta-analysis aimed to evaluate the efficacy and safety of different adjustable slings compared to other surgical methods in the treatment of SUI among women. All currently available data were summarized and analyzed. Data from 18 clinical trials, including 14 RCTs, were included. All of these studies assessed the patient’s quality of life and their subjective and objective satisfaction after treatment. This study shows that adjustable SIMS demonstrates equal efficacy compared with SMUS for the treatment of SUI among women. Moreover, the operation time of the adjustable SIMS was lower.

According to the International Continence Society Standards 2020–2021 [40], complications after the use of mesh, bands, and grafts in female pelvic surgery may include local complications, complications affecting surrounding organs, and systemic complications. These complications may be symptomatic or asymptomatic, may be due to infections or abscesses, and may involve vaginal localization, urinary tract, rectum or bowel, skin, and musculoskeletal or systemic effects. These safety concerns have contributed to new approaches to decrease complication rates.

Adequate tension of the tape is critical for achieving sufficient continence while avoiding bladder outlet obstruction (BOO). Following the results from Park et al., more than 80% of surgeons considered sling tension to be important or very important [41]. According to a Cochrane systematic review, the average risk of BOO after TOT is approximately 4.0% [2]. Blaivas et al. [7] found an average rate of BOO of 5.9% (0–33.9%) after TOT, with an average rate of surgical treatment for postoperative BOO of 2.3% (0–21.3%) [18]. If the sling tension is insufficient, the incontinence may persist. Adjustable slings are aimed at reducing the abovementioned complications. In many papers on adjustable slings, there is a comparison of one adjustable sling to another sling/sling. In this meta-analysis, different adjustable slings were compared with other surgical methods for the treatment of SUI among women.

The lack of standardized measures for continence surgery makes it difficult to compare different treatment options with regard to effectiveness and, essentially, safety. Thus, this systematic review and meta-analysis has a number of limitations, including the poor quality of some of the included studies. Most of the included studies had a small sample size and were published long ago. Additionally, few of the included studies were of high quality. All these limitations were a sources of high heterogeneity in the current meta-analyses as well as a high risk of bias (critical or high risk of bias). Finally, adjustable slings are a diverse type of surgical treatment, thus making comparisons difficult. Regarding implications for future research, more accurately conducted prospective and randomized trials are required to evaluate the advantages and disadvantages of adjustable slings and other surgical treatments. Clinical studies should have a large sample size and long-term follow-up to provide a comprehensive view on the issue of adjustable slings in the surgical treatment of SUI. Moreover, studies should have common standardized measures for continence surgery to make the results more objective.

Conclusion

Safety concerns regarding surgical treatment of SUI have contributed to the development of new approaches to decrease complication rates. This systematic review and meta-analysis shows that adjustable SIMS demonstrates equal efficacy compared with SMUS for the treatment of SUI among women. Moreover, the operation time of the adjustable SIMS was lower. Nevertheless, more accurately conducted studies with standard outcome measures and complete follow-up periods will help to increase confidence in the choice of different options for treating SUI among female patients.